1. Field of the Invention
The present invention relates to a process for smoothing the curves generated by a graphic visualization system of the black and white and color television scanning type.
Generally it is known that the visualization surface of such a system may be divided into an assembly of small fictitious squares called picture elements or "pixels" referenced by the coordinates of their center (X, Y). Usually, an infinite number of pixel positions on the screen corresponds to a given visualization surface and to a given memory size.
These elements are divided up according to a grid (mesh network) whose pitch is given by the distance between two pixels. Thus, the reproduction or even the formation of an image may be obtained by causing, through scanning, a corresponding number of pixels to be illuminated to which a given luminance and, possibly, chrominance are assigned.
The invention relates more particularly, but not exclusively, to a process for smoothing curves generated by a television scanning system, in which the computation of the dots of the screen to be illuminated may be achieved essentially by means of additions and shifts.
Numerous solutions have already been proposed to this end. However, it is proved that, in these known methods of generation, the curves obtained are formed by successions of horizontal or vertical segments (depending on the slope of the curve) off-set with respect to one another while forming staircase steps.
To overcome this disadvantage, it is then advisable to smooth the curve obtained by local reduction of the contrast between the line and the background and by artificially increasing the definition of the image.
2. Description of the Prior Art
There has already been proposed for resolving this problem, more especially by the patent No. FR 2 371 031, a process consisting in representing each point of the curve by adjusting the relative luminosity of a matrix of display elements adjacent the position required for this point of the curve, so that this group of display elements creates a subjective impression of this point of the curve, in its desired position. This process uses more particularly a memory which stores all the possible luminosity contributions required for each display element and an addressing device which reads from the memory, in response to input signals defining the real positions of the points of the curve, the real contributions required for the luminosity of this element. This process has however proved to be relatively complex and requires, for implementation thereof, a relatively powerful processor equipped with large capacity memories.
The invention has then more particularly as its object to provide a process of simple conception using memory spaces of much smaller size and which allows smoothed black and white or color images having a good definition to be obtained despite everything.